Previously, active pharmaceutical ingredient and diluent had to be provided in separate containers, and the contents of the separate containers needed to be brought together, e.g. in a vial or a syringe, in order to mix the contents prior to delivering the mixed drug. Thus, in prior art systems, the diluent, the active pharmaceutical ingredient and the mixing volume need to be kept under sterile conditions. Furthermore there is a risk that the active pharmaceutical ingredient and the diluent are not properly mixed.